1. Field of the Invention
The present invention relates to a machine tool provided with a universal head.
2. Description of the Related Art
As a machining head of a machining center or other machine tool, there is known a universal head holding a spindle for rotating a tool so as to be able to swivel to a plurality of directions so as to increase the freedom of the machining posture of the tool.
This universal head, for example, is provided with a swivel unit held by a head or ram to be able to swivel in a horizontal plane about a predetermined axis and a tool mount held by the swivel unit to be able to swivel along a vertical plane, rotatably holding a spindle mounting a tool at its front end, and having a built-in motor for directly driving the spindle.
The universal head machines a workpiece by mounting a tool at the front end of the spindle and suitably indexing the swivel positions of the swivel unit and the tool mount while rotating the spindle.
In the above universal head, however, there is the disadvantage that routing the cable for supplying power to the built-in motor driving the spindle becomes complicated. That is, the cable for supplying power to the built-in motor is connected to the built-in motor provided in the tool mount from the ram or head side through the swivel unit.
Therefore, it is difficult to enable the swivel unit to swivel by 360 degrees or more with respect to the ram or head. If the swivel unit cannot swivel by 360 degrees or more, for example the tool cannot be made to contact the entire outer circumference of the workpiece by a swivel operation of the swivel unit.
In this way, there was the disadvantage that the range of operation of the swivel unit was restricted by the presence of the cable for supplying power to the built-in motor.
An object of the present invention is to provide a machine tool provided with a universal head free from restrictions on its swivel operation due to the presence of a power cable to a motor directly driving a spindle and consequently expanded in range of movement.
To attain the above object, there is provided a machine tool having a support; a swivel unit held at the support to be able to swivel about a predetermined axis; a tool mount held at the swivel unit, rotatably holding at its front end a spindle to which a tool is mounted, and provided with a motor for driving the spindle; a generator provided at the swivel unit and generating power used by the motor; and a power source provided at the support and supplying power to the generator.
Preferably, the power source comprises a motor built into the support, an output shaft of the motor and an input shaft of the generator are connected, and the output shaft and input shaft are concentric with the axis.
Preferably, the tool mount is held at the swivel unit to be able to swivel about a predetermined axis.
In the present invention, the generator provided at the swivel unit is supplied with power from a power source provided at the support and generates electric power. The electric power generated by the generator is supplied to the motor provided at the tool mount to drive the spindle and rotate the tool. In this way, there is no power cable between the support and the swivel unit held at the support to be able to swivel, so the range of swivel of the swivel unit is not restricted.